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Monday, March 14, 2011

FCI could be a BFD

If the nuclear plants in Japan really do melt down, apparently it could be due to something called a "fuel-coolant interaction," or "FCI," in which superheated, molten nuclear fuel hits cooling water (which now is apparently seawater) at the bottom of the reactor vessel and causes a steam explosion. A fat reactor safety training course, put together by the U.S. Nuclear Regulatory Commission in 2002, spends quite a bit of time on this possibility. You can read all about it on pages 228 to 246 (the last 19 pages) of this large pdf file (excerpted here).

The Wiki condensation of this material isn't that much easier to understand, but it says:

At the point at which the corium relocates to the lower plenum, Haskin, et al relate that the possibility exists for an incident called a fuel-coolant interaction (FCI) to substantially stress or breach the primary pressure boundary when the corium relocates to the lower plenum of the RPV [reactor pressure vessel]. This is because the lower plenum of the RPV may have a substantial quantity of water -- the reactor coolant -- in it, and, assuming the primary system has not been depressurized, the water will likely be in the liquid phase, and consequently dense, and at a vastly lower temperature than the corium. Since corium is a liquid metal-ceramic eutectic at temperatures of 2,200 to 3,200 K (3,500 to 5,300 °F), its fall into liquid water at 550 to 600 K (530 to 620 °F) may cause an extremely rapid evolution of steam that could cause a sudden extreme overpressure and consequent gross structural failure of the primary system or RPV. Though most modern studies hold that it is physically infeasible, or at least extraordinarily unlikely, Haskin, et al state that that there exists a remote possibility of an extremely violent FCI leading to something referred to as an alpha-mode failure, or the gross failure of the RPV itself, and subsequent ejection of the upper plenum of the RPV as a missile against the inside of the containment, which would likely lead to the failure of the containment and release of the fission products of the core to the outside environment without any substantial decay having taken place.

However, it is likely, as in the Three Mile Island accident, that any FCI that occurs will not substantially breach the primary pressure boundary, or lead to the gross structural failure of the primary system or RPV, and the corium will reach the lower plenum with the lower plenum remaining intact.

And if you throw ocean water into the mix, for days or months on end, will that make any difference? We doubt that anybody knows.

Comments (18)

The biggest issue with using seawater as coolant, is that the salt will corrode the steel core over time. This will only be a problem far after the current issues are taken care of, because it won't allow them to restart the reactor.

I think we're well past the point of thinking this core could ever restart anyway, so pump in the seawater and keep the pile cool until you can pull the whole vessel out as one piece and inter it somewhere permanently.

Keeping the pile cool until you can pull the whole vessel out is a rather long term process. look how long spent rods need to be under water. But there is likely no other alternative, and this in a tsunami prone zone.

The flawed thinking in the placement of the plants, the seawall and the confidence in that sea wall which governed the over all planning for an emergency is breathtaking, the falsification of theories guiding these decisions, overwhelming.

As far as I can tell from reading any and all reports I can find I think that the truth is that no one knows what the heck is going on.
The buildings are severly damaged, so all of the monitoring systems and cameras etc are gone; it is WAG time.
So stay calm everyone....sarcasm alert....and trust the gubbmint to tell the truth about what is.
Excuse me I have to go and find my tin foil hat now. Oh wait....no TIN foil...I guess I will have to make do with aluminum.
But seriously, how do we the people demand the truth about this situation?

Can you imagine the supervisor-worker relationships in that plant right now? I bet senior management is huddled in some bunker ordering the less senior types to do this or that for the sake of the company and honor and Japan, etc...I just wonder if the point will come when the workers say, "Here's my 2-week notice effective 2 weeks ago" and book.
One radio interview was with a woman whose husband worked at the plant. He described the collapse of the roof, etc... to her. Then she said, he jumped in his car with some other workers and got the hell out.
I wonder how many workers are still there?

Where are all the pro-nuke cheerleaders telling us how safe the industry is?

Im not really "pro-nuke" but is it any less safe than other industrial plants?
It was a "once in 500 years" event that damaged the plant. That could happen anywhere, to any kind of industrial plant.
We should be thankful they all didnt just crumble to pieces. They were designed to handle a 7 magnitude quake, and have fared pretty well after a 9.

What if Bonneville Dam failed from an earthquake? Im sure that would be pretty bad for folks downstream as well.

Below I reproduce a summary on the situation prepared by Dr Josef Oehmen, a research scientist at MIT, in Boston. He is a PhD Scientist, whose father has extensive experience in Germany’s nuclear industry. This was first posted by Jason Morgan earlier this evening, and he has kindly allowed me to reproduce it here. I think it is very important that this information be widely understood.

...
The plant came close to a core meltdown. Here is the worst-case scenario that was avoided: If the seawater could not have been used for treatment, the operators would have continued to vent the water steam to avoid pressure buildup. The third containment would then have been completely sealed to allow the core meltdown to happen without releasing radioactive material. After the meltdown, there would have been a waiting period for the intermediate radioactive materials to decay inside the reactor, and all radioactive particles to settle on a surface inside the containment. The cooling system would have been restored eventually, and the molten core cooled to a manageable temperature. The containment would have been cleaned up on the inside. Then a messy job of removing the molten core from the containment would have begun, packing the (now solid again) fuel bit by bit into transportation containers to be shipped to processing plants. Depending on the damage, the block of the plant would then either be repaired or dismantled.
.....

If you want to stay informed, please forget the usual media outlets and consult the following websites:

Over 50% of the reactor core at Three Mile Island melted down. Containment was never lost. No person suffered harm.

While the news reports from Japan regarding the reactors are interesting, it's the body count from the tsunami itself that's depressing. Thousands are washing back up; the country's out of body bags, and crematoria working 24/7 can't keep up.

All the articles I've read say that if one or more reactors does meltdown to the containment shell, they will pour concrete on it to contain it. Can anyone explain why they are not just pouring concrete on it now?

Road Work

Miles run year to date: 155
At this date last year: 241
Total run in 2015: 271
In 2014: 401
In 2013: 257
In 2012: 129
In 2011: 113
In 2010: 125
In 2009: 67
In 2008: 28
In 2007: 113
In 2006: 100
In 2005: 149
In 2004: 204
In 2003: 269